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. 2021 Apr 9;19(1):89.
doi: 10.1186/s12916-021-01967-w.

Modeling the interplay between demography, social contact patterns, and SARS-CoV-2 transmission in the South West Shewa Zone of Oromia Region, Ethiopia

Filippo Trentini  1 , Giorgio Guzzetta  1 , Margherita Galli  1   2 , Agnese Zardini  1   3 , Fabio Manenti  4 , Giovanni Putoto  4 , Valentina Marziano  1 , Worku Nigussa Gamshie  5 , Ademe Tsegaye  6 , Alessandro Greblo  4 , Alessia Melegaro  7   8 , Marco Ajelli  9   10 , Stefano Merler  1 , Piero Poletti  11
Affiliations

Modeling the interplay between demography, social contact patterns, and SARS-CoV-2 transmission in the South West Shewa Zone of Oromia Region, Ethiopia

Filippo Trentini et al. BMC Med. .

Abstract

Background: COVID-19 spread may have a dramatic impact in countries with vulnerable economies and limited availability of, and access to, healthcare resources and infrastructures. However, in sub-Saharan Africa, a low prevalence and mortality have been observed so far.

Methods: We collected data on individuals' social contacts in the South West Shewa Zone (SWSZ) of Ethiopia across geographical contexts characterized by heterogeneous population density, work and travel opportunities, and access to primary care. We assessed how socio-demographic factors and observed mixing patterns can influence the COVID-19 disease burden, by simulating SARS-CoV-2 transmission in remote settlements, rural villages, and urban neighborhoods, under school closure mandate.

Results: From national surveillance data, we estimated a net reproduction number of 1.62 (95% CI 1.55-1.70). We found that, at the end of an epidemic mitigated by school closure alone, 10-15% of the population residing in the SWSZ would have been symptomatic and 0.3-0.4% of the population would require mechanical ventilation and/or possibly result in a fatal outcome. Higher infection attack rates are expected in more urbanized areas, but the highest incidence of critical disease is expected in remote subsistence farming settlements. School closure contributed to reduce the reproduction number by 49% and the attack rate of infections by 28-34%.

Conclusions: Our results suggest that the relatively low burden of COVID-19 in Ethiopia observed so far may depend on social mixing patterns, underlying demography, and the enacted school closures. Our findings highlight that socio-demographic factors can also determine marked heterogeneities across different geographical contexts within the same region, and they contribute to understand why sub-Saharan Africa is experiencing a relatively lower attack rate of severe cases compared to high-income countries.

Keywords: COVID-19; Contact data; Contact matrix; Epidemic; Mixing patterns; Rural; SARS-CoV-2; Transmission model; Urban.

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Conflict of interest statement

MA has received research funding from Seqirus. The funding is not related to COVID-19. All other authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Contact matrix representing the mean number of daily contacts reported by a participant in the age group i with individuals in the age group j in household (a), in the general community (b), and both (c) in remote settlements. d–f, g–i The same quantities estimated for rural villages and for the urban neighborhoods, respectively
Fig. 2
Fig. 2
Estimated attack rates of infection (a), symptomatic cases (b), and critical disease (c), overall and by age group in different geographical contexts of the SWSZ, as expected at the end of an epidemic mitigated by school closure alone. Outputs were obtained by simulating 1000 different epidemics where the per-contact transmission rate is set to reproduce, when neglecting contacts occurring at school, random samples of the distribution of the net reproduction number estimated from national surveillance data: 1.62 (95% CI 1.55–1.70) [5]. Black lines represent 95% credible intervals
Fig. 3
Fig. 3
Estimated percentage of a averted infections, b symptomatic infections, and c critical cases, overall and by age group in different geographical contexts of the SWSZ with respect to a hypothetical scenario without school closure. Black lines represent 95% credible intervals
Fig. 4
Fig. 4
Comparison of the estimated overall percentage of critical cases in different geographical contexts of the SWSZ in the baseline and sensitivity analyses. Black lines represent 95% credible intervals
See this image and copyright information in PMC

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